Clamp with preset tension



Aug- 22 1967A H. ARMAcosT 3,336,642

CLAMP WITH PRESET TENSION Filed oct. 19, 1965 /Po erfr/navas INVENTOR.

BY ael'er f ran/ law,

- out from its location United States Patent O 3,336,642 CLAMP WITH PRESET TENSION Robert H. Armacost, Los Angeles, Calif., assignor to American Drill Bushing Co., Los Angeles, Calif., a corporation of Maryland Filed Oct. 19, 1965, Ser. No. 498,022 4 Claims. (Cl. 24-263) The invention relates to clamps of the character of C clamps, but more particularly a convenient clamp for one hand operation which applies a preset tension to whatever may be clamped.

Although C clamps have been iu common use for a great many years, most conventional clamps of this kind depend upon the operator for the amount of tension exerted by the clamp. While for many operations tension of course can be adjusted by feel and whereas for delicate operations some appropriate torque limiting device could be employed on the handle, C clamps for the most part are shop devices which need to be applied quickly and easily by hand application for purely temporary use.

In some types of gluing operations, and especially Where epoxy resin glues are concerned, it becomes very advantageous to have pressure carefully applied when one sheet of material is to be glued to another. If too much pressure is applied, too much of the glue will be squeezed between the sheets of material and a nondependable adhesion will be the result. If insufficient pressure is applied by such a device as a C clamp, too much glue may remain and the resulting lamination of sheets may, for example, be too thick and need sizing or the glue, if something other than an epoxy resin, may not bond properly. Moreover, when a workman vis working rapidly with a quick setting glue, for example, it is not always possible or advantageous to carefully adjust each of a large number of C clamps for fastening multiple sheets of material to be laminated together and the work is considerably slowed down if all tension adjustments made must be made by hand.

It is therefore among the objects of the invention to provide a new and improved clamp which is capable of exerting a preset tension on material to be clamped such as multiple sheets which are to be laminated together.

Another object of the invention is to provide a new and improved clamp device which can be applied with one hand.

Still another object of the invention is to provide a new and improved clamp device which is snug in its configuration so that when used either singly or in multiple numbers side by side it will be fastened relatively close to the work and not be easily knocked loose.

Still another object of the invention is to provide a new and improved clamp device for presetting tension on a device to be clamped which is simple and positive in its operation and which is relatively inexpensive to manufacture and assemble. v

Still another object of the invention is to provide a new and improved preset clamp device so specially arranged that the preset tension can be applied to a warped surface just as readily as to a sheet of material opposite sides of which are perfectly parallel.

With these and other objects in view, the invention consists in the construction, arrangement, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter set forth, pointed out in the appended claims and illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is aside elevational view of one form of the device.

FIGURE 2 is a longitudinal sectional view of the device of FIGURE 1 shown applied to a workpiece.

FIGURE 3 is a cross-sectional view on the line 3-3 of FIGURE 2.

FIGURE 4 is a side elevational View partially broken away showing a second form of the invention.

In an embodiment of the invention chosen for the purpose of illustration there is shown a frame indicated generally by the reference character 10 which consists of a lower bracket arm 11 and an upper bracket arm 12 in substantially parallel relationship and joined at respective ends by a connecting handle 13. A guide arm has a horizontal portion 14 and a connecting portion 15 whereby the guide arm is attached to the bracket arm 12 at the end opposite from the handle 13. The bracket arm 11 is provided at its clamping end 16 with a clamping surface 17 which may, if desired, be merely the upper surface of the bracket arm.

A shaft 20 extends through a square hole 21 in the bracket arm 12 and an aligned square hole 22 in the horizontal portion 14 of the guide arm. The shaft 20 is thus slidably Ibut nonrotatably mounted upon the frame 10. A pad indicated generally by the reference character 23 is provided with a plastic contact shoe 24 applied over a head 25. The head is secured to the shaft 20 by a threaded end 26 to bias the pad 23 in a position normally exerting pressure upon a workpiece 27. Use is made of a spring 28 which presses at its lower end against the head 25 and at its upper end against the under surface of the bracket arm 12. The workpiece is shown as one consisting of a central sheet 29 to which is laminated an upper sheet 30 and a lower sheet 31.

To lift the pad 23 use is made of a lifter indicated generally by the reference character 35. One end 36 of the lifter is pivotally secured by means of a pin 37 in a recess 38 in the shaft 20. The other end 39 of the lifter terminates in a thumb-piece 40. The end 39, if desired, may be slightly longer than the end 36 depending upon the mechanical advantage desired. Intermediate the ends 36 and 39 at a corner 41 of the lifter is a pair of rollers,42 and 42', rotatably secured to the corner by means of a pin 43. The Irollers are free to roll along the upper surface of the bracket arm 12 when the lifter is rocked about the axis of rotation of the pin 43.

In use the frame is grasped by wrapping three or four lingers of the hand around the handle 31 in position such that the thumb rests upon the thumbpiece 40. The thumbpiece is then depressed as far as it will go in order to lift the pad 23 to its uppermost position. Preferably there should Ibe a quarter inch to of an inch clearance between the lower face of the shoe 24 and the sheet 30, for example, although this distance is not critical. Even though there may be some variation in the tension exerted by the spring 28 when fully compressed as compared to partially extended, the difference is not critical and hence the clearance is not critical. When the pad 23 is in proper position with respect to the workpiece, the thumbpiece 40 is released and the spring 28 then presses the pad 23 against the workpiece as shown in FIGURE 2.

When there is likelihood that the surface of the workpiece may be tilted or warped, use is made of pads 45 and 46 as illustrated in FIGURE 4. The pad 45 in this example consists of a head 47 in which is a rounded recess 48 which accommodates a ball 49 extending from a lower end of the shaft 20. A cap 50 in threaded engagement with the head 47 .has an aperture 51 at the top which accommodates a shank 52 with an adequate clearance so that when a shoe 53 attached to the lower end of the head 47 tilts, an ample degree of tilt will be permitted Without binding.

The pad 46 is similarly constructed, consisting as shown of a head 54 provided with a rounded recess 55 for the accommodation of a ball 56. The ball is on a pedestal 57 riveted at 58 to the clamping end 16 of the frame. An appropriate aperture 58 allows for the necessary angular tilt when a shoe S9 engages a tilted or warped surface when in use. The device of FIGURE 4 is manipulated by the same lifter 35 as has been described in connection with FIGURES 1, 2, and 3.

From the specification and drawings it will be appreciated that the frame 10 can be a stamping easily cut out and bent to the form shown and that the lifter 35 may also be a stamping. The shaft 20, preferably a square shaft to prevent rotation and thereby keep the rollers in position, can be of any commercial square rod cut to size and threaded at 26 for the accommodation of the pad 23. Pads 45 and 46 can be identical, if desired, or of different sizes as the case may require. Although two pads are shown in the form of the invention of FIGURE 4, occasions may suggest that only one pad be used attached either to the bracket arm 11 or in the alternative to the shaft It has been found in practice that small clamps capable of exerting an eight pound pressure are eX- tremely useful in the lamination of synthetic plastic resin material. The preset tension, however, can be varied considerably depending upon the size of clamp made use of and the character of the spring 28. Should the same clamp be needed for work requiring different tension, different springs may be substituted as occasion requires.

While the invention has herein been shown and described in what is conceived to be the most practical and preferred emobdiment, it is recognized that departures may be made therefrom within the scope of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices.

Having described the invention, what is claimed as new in support of Letters Patent is:

1. A pressure clamp for exerting a predetermined pressure on a sheet of material comprising a frame having spaced bracket arms with clamping ends opposite each other, a connecting handle attached to said arms, a guide member adjacent one of said bracket arms and an operating assembly comprising a shaft extending slidably and nonrotatably through said guide member and Said one bracket arm, a spring acting between said shaft and said frame biased to extend said shaft toward said other bracket arm, and a lifter comprising a first end element movably connected to said shaft, a second end element having a thumbpiece thereon and a contact element intermediate said end elements having a moving engagement with said one bracket arm.

2. A pressure clamp for exerting a predetermined fixed pressure on a sheet of material comprising a frame having spaced bracket arms with clamping ends opposite each other, a connecting handle attached to said arms, a guide member adjacent one of said bracket arms, and an operating assembly comprising a shaft extending slidably and nonrotatably through said guide member and said one bracket arm, a spring between said shaft and said frame biased to extend said shaft toward said other bracket arm, and a lifter comprising a first end element pivotally connected to said shaft, a second end element having a thumbpiece thereon and a roller intermediate said end elements in rolling engagement with said one bracket arm.

3. A pressure clamp for exerting a predetermined pressure on a sheet of material comprising a frame having spaced bracket arms with clamping ends opposite each other, a connecting handle attached to said arms at respective ends of said arms opposite said clamping ends, a guide arm adjacent to and spaced from one of said bracket arms and an operator assembly comprising a shaft extending slidably and nonrotatably through said guide arm and said one bracket arm, a pressure element on one end of said shaft, a spring acting between said shaft and said frame biased to extend said pressure element toward said other bracket arm, and a lifter comprising a first end element pivotally connected to said shaft, a second end element having a thumbpiece thereon and a low friction element intermediate end elements having a low friction engagement with said one bracket arm.

4. A pressure clamp for exerting a predetermined fixed pressure on a laminated sheet of materials comprising a frame having spaced, substantially parallel bracket arms with clamping ends opposite each other, a connecting handle attached to said arms at respective ends of said arms opposite said clamping ends, a guide arm adjacent to and spaced from one of said bracket arms and an operating assembly comprising a shaft extending slidably and nonrotatably through said guide arm and said one bracket arm, a pressure pad having a connection to one end of said shaft, and a spring acting between said shaft and said one bracket arm biased to extend said pad toward the other bracket arm, a pad having a connection to said other bracket arm opposite said first identified pad, and a lifter comprising a first end element pivotally connected to said shaft, a second end element having a thumbpiece thereon and a roller intermediate said end elements having a rolling engagement with said one bracket arm, at least One of said connections comprising a universal joint whereby to adapt said pad to an irregular surface on said sheet of materials.

References Cited UNITED STATES PATENTS 785,432 3/ 1905 Perkins.

865,444 9/1907 Staley 269--143 X 1,203,209 10/1916 Lawson 14A-307 1,774,267 8/1930 Hanke 24-263 2,316,290 4/1943 Schcnbeck 24-263 X 2,490,923 12/1949 Sasgen 269-143 3,151,897 10/1964 Wagner 269-258 X WILLIAM FELDMAN, Primary Examiner.

DONALD A. GRIFFIN, Examiner. 

1. A PRESSURE CLAMP FOR EXERTING A PREDETERMINED PRESSURE ON A SHEET OF MATERIAL COMPRISING A FRAME HAVING SPACED BRACKET ARMS WITH CLAMPING ENDS OPPOSITE EACH OTHER, A CONNECTING HANDLE ATTACHED TO SAID ARMS, A GUIDE MEMBER ADJACENT ONE OF SAID BRACKET ARMS AND AN OPERATING ASSEMBLY COMPRISING A SHAFT EXTENDING SLIDABLY AND NONROTATABLY THROUGH SAID GUIDE MEMBER AND SAID ONE BRACKET ARM, A SPRING ACTING BETWEEN SAID SHAFT AND SAID FRAME BIASED TO EXTEND SAID SHAFT TOWARD SAID OTHER BRACKET ARM, AND LIFTER COMPRISING A FIRST END ELEMENT MOVABLY CONNECTED TO SAID SHAFT, A SECOND END ELEMENT HAVING A THUMBPIECE THEREON AND A CONTACT ELEMENT INTERMEDIATE SAID END ELEMENTS HAVING A MOVING ENGAGEMENT WITH SAID ONE BRACKET ARM. 